Guerbet alcohols are primary alcohols branched in the 2-position which are obtained by condensation of linear fatty alcohols. The products are mainly used as oil components for the production of cosmetic emulsions. They are generally produced from fatty alcohols which, initially, self-condense under the effect of strong bases and heavy metal compounds, for example copper or zinc oxide. It is assumed that, under the reaction conditions, the alcohol is first dehydrogenated to the aldehyde which enters into an aldol condensation with itself, after which the condensation product is hydrogenated to the alcohol. A corresponding overview can be found, for example, in Angew. Chem. 64, 212 (1952). Dialkyl cyclohexanes are similarly produced by double condensation of fatty alcohols with cyclohexanol in the presence of heavy metals.
However, a disadvantage is that, after the reaction, the heavy metal catalysts have to be removed in order to meet legal requirements and to ensure that they do not cause any irritation in the subsequent application. The heavy metal catalysts are generally removed by washing and subsequent distillation which involves considerable product losses. Another disadvantage is that the reaction times are very long and the selectivities are unsatisfactory.